In the common hair shaping processes the hair is at first treated with the watery solution of a reducing compound, in particular a mercapto compound, above all with thioglycolate in an alkaline medium or with a sulfite, preferably in a weak acid to neutral medium. Thereby, the disulfide bridge compounds of the hair keratine are split due to chemical separation and the hair is accessible to a permanent shaping.
The practical operation of the permanent shaping of human hair is generally performed in accordance with two variations. In accordance with one variation, the washed and towel dry hair is at first parted into a plurality of sections, thereafter these sections are pre-wetted with a portion of a liquid permanent shaping medium and finally the hair is then rolled onto rollers. After finishing the roller operation, the rollers are then afterwetted with the remainder of the liquid permanent shaping medium. In the other variation, the hair is also parted into a plurality of sections, after a preceeding hair washing and thereafter the hair is rolled on rollers without prewetting with a permanent shaping medium. After finishing rolling the hair onto the rollers, the rollers are thoroughly wetted with the total required quantity of the permanent shaping medium. The rollers being used for a permanent curling have a diameter of about 5 to 13 millimeter, while for a decurling rollers are required which have a diameter above 13 millimeter.
The reaction time of the hair shaping medium on the hair during the permanent curling as well as the permanent decurling takes up to about 30 minutes depending on the condition of the hair and the desired degree of shaping. The reaction time can be shortened by means of a heat supply, for example, by using a heat radiator or a hair drier.
After the duration of the required reaction time of the hair shaping medium the rolled up hair is rinsed with water and is fixed into the new shape with the watery solution of an oxidation medium, preferably with a 2% hydrogen peroxide solution, while again reestablishing the previously split disulfide compounds of the hair keratine.
Thereby, the reaction time of the fixing medium is generally 10 to 15 minutes. Finally, the rollers are removed and the hair is thoroughly rinsed with water. During the reaction time of the hair shaping medium and in particular when supplying heat, a large part of the ammonia, present as an alkalisation medium in the preparations, escapes. Furthermore, portions of the mercapto compound or the sulfite, contained as reductive acting permanent shaping ingredients, are oxidized by the atmospheric oxygen, due to the large surface of the hair. It the hair-shaping medium is acid adjusted, a decomposition of the wave shaping ingredient can occur with a separation of foul smelling hydrogen sulfide. The missing screening for the rollers finally results in a loss of liquid and heat. Naturally, the mentioned effects are stronger on the outer layers of the rolled up hair, that is, in the area of the hair close to the head than in the inner layers of the hair. Consequently, the permanent shaping in the area of the hair in close proximity to the head is unsatisfactory. If, in contrast thereto, one would prolong the reaction time or select a stronger, more effective shaping medium, one would obtain a sufficient shaping of the hair in the proximity to the head; however the tips of the hair would be damaged.
This negative result is also increased because the tips of the hair are more sensitive to chemical reactions than the hair in the proximity of the head. In addition, the tips of the hair are at first rolled onto the roller and are therefore curled more strongly than the beginning of the hair at the proximity of the head, which is superimposed on tips of the hair.
However, it is the aim of a permanent hair shaping to obtain a uniform shaping of the hair, from the tips of the hair to the beginning of the hair, without damaging the tips of the hair.
A screening of the rollers can be obtained by using a foam like permanent shaping medium. Thereby, a closed stable foam layer is applied onto the rollers. However, thereby the unavoidable simultaneous wetting of the scalp as well as the uncontrollable running off of the shaping liquid from the decomposing foam is disadvantageous.
With the screening of the rollers recommended in the German laid open patent No. 2,822,125 by means of a layer of a finely granulated solid material or by covering the hair with a plastic cover, a certain success with respect to screening is obtained, however the different sensitivity of the hair between the beginning of the hair and the tips of the hair with respect to a chemical shaping is thereby not equalized.